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Selective breeding strategies require pedigree information over generations, but many species produced in aquaculture are too small to be physically tagged at early stages. Consequently, maintaining a sufficient number of separate families is often needed but costly and logistically difficult. Alternatively, parentage assignment can be obtained using DNA markers. We developed a panel of single nucleotide polymorphism (SNP) markers for the European abalone Haliotis tuberculata using an existing transcriptomic resource. An initial set of 2,176,887 SNPs was filtered to select 500 for high throughput genotyping. Of these, 298 SNPs were amplified in at least 90% of our H. tuberculata samples, consisting of a mixed family cohort (945 offspring) generated by crossing 40 abalones, and 5 full-sib training families (70 offspring). Based on amplification success among parents, minimum allele frequency and checks carried out against the training families, a subset of 123 markers was used to carry out parentage assignment in our mixed family cohorts. Maximum likelihood and exclusion-based methods of parentage assignment yielded consistent results, allowing parentage to be assigned in 98.9% of the studied progeny. Optimization of markers suggests that the 60 most informative SNPs may be sufficient for 95% assignment success in these progeny. The panel was also used to estimate effective population size, and revealed a low Ne due to high variance of reproductive success between parents. Our panel could be used to estimate genetic parameters of traits in mixed family cohorts, an essential stage to initiate selective breeding in H. tuberculata. It could also be useful tool in the context of monitoring stock enhancement and population genetics studies.

Selective breeding strategies require pedigree information over generations, but many species produced in aquaculture are too small to be physically tagged at early stages. Consequently, maintaining a sufficient number of separate families is often needed but costly and logistically difficult. Alternatively, parentage assignment can be obtained using DNA markers. We developed a panel of single nucleotide polymorphism (SNP) markers for the European abalone Haliotis tuberculata using an existing transcriptomic resource. An initial set of 2,176,887 SNPs was filtered to select 500 for high throughput genotyping. Of these, 298 SNPs were amplified in at least 90% of our H. tuberculata samples, consisting of a mixed family cohort (945 offspring) generated by crossing 40 abalones, and 5 full-sib training families (70 offspring). Based on amplification success among parents, minimum allele frequency and checks carried out against the training families, a subset of 123 markers was used to carry out parentage assignment in our mixed family cohorts. Maximum likelihood and exclusion-based methods of parentage assignment yielded consistent results, allowing parentage to be assigned in 98.9% of the studied progeny. Optimization of markers suggests that the 60 most informative SNPs may be sufficient for 95% assignment success in these progeny. The panel was also used to estimate effective population size, and revealed a low Ne due to high variance of reproductive success between parents. Our panel could be used to estimate genetic parameters of traits in mixed family cohorts, an essential stage to initiate selective breeding in H. tuberculata. It could also be useful tool in the context of monitoring stock enhancement and population genetics studies.

Selective breeding strategies require pedigree information over generations, but many species produced in aquaculture are too small to be physically tagged at early stages. Consequently, maintaining a sufficient number of separate families is often needed but costly and logistically difficult. Alternatively, parentage assignment can be obtained using DNA markers. We developed a panel of single nucleotide polymorphism (SNP) markers for the European abalone Haliotis tuberculata using an existing transcriptomic resource. An initial set of 2,176,887 SNPs was filtered to select 500 for high throughput genotyping. Of these, 298 SNPs were amplified in at least 90% of our H. tuberculata samples, consisting of a mixed family cohort (945 offspring) generated by crossing 40 abalones, and 5 full-sib training families (70 offspring). Based on amplification success among parents, minimum allele frequency and checks carried out against the training families, a subset of 123 markers was used to carry out parentage assignment in our mixed family cohorts. Maximum likelihood and exclusion-based methods of parentage assignment yielded consistent results, allowing parentage to be assigned in 98.9% of the studied progeny. Optimization of markers suggests that the 60 most informative SNPs may be sufficient for 95% assignment success in these progeny. The panel was also used to estimate effective population size, and revealed a low Ne due to high variance of reproductive success between parents. Our panel could be used to estimate genetic parameters of traits in mixed family cohorts, an essential stage to initiate selective breeding in H. tuberculata. It could also be useful tool in the context of monitoring stock enhancement and population genetics studies.

Dinoflagellates of the genus Alexandrium are a major cause of harmful algal blooms (HABs) that have increasingly disrupted coastal ecosystems for the last several decades. Microalgae from the genus Alexandrium are known to produce paralytic shellfish toxins (PST) but also bioactive extracellular compounds (BEC) that can display cytotoxic, allelopathic, ichtyotoxic or haemolytic effects upon marine organisms. The objective of this experimental study was to assess the effects of PST and BEC produced by A. minutum upon juvenile great scallops Pecten maximus. Scallops were exposed for one week to two different strains of A. minutum, the first producing both PST and BEC and the second producing only BEC. Escape response to starfish, daily shell growth, histological effects, and accumulation of PST were recorded after one week of exposure, and after two subsequent weeks of recovery. Daily shell growth was delayed three days in scallops exposed to the BEC-producing A. minutum strain, probably during the three first days of exposure. An increase of reaction time to predators was observed in scallops exposed to the BEC condition, suggesting that BEC may have altered sensing processes. Scallops exposed to PST displayed a less-efficient escape response and muscular damage which could reflect the effects of paralytic toxins upon the nervous system of scallops. This study demonstrates contrasting effects of the distinct toxic compounds produced by A. minutum upon marine bivalves, thus highlighting the importance to better characterize these extracellular, bioactive compounds to better understand responses of other marine organisms.

Dinoflagellates of the genus Alexandrium are a major cause of harmful algal blooms (HABs) that have increasingly disrupted coastal ecosystems for the last several decades. Microalgae from the genus Alexandrium are known to produce paralytic shellfish toxins (PST) but also bioactive extracellular compounds (BEC) that can display cytotoxic, allelopathic, ichtyotoxic or haemolytic effects upon marine organisms. The objective of this experimental study was to assess the effects of PST and BEC produced by A. minutum upon juvenile great scallops Pecten maximus. Scallops were exposed for one week to two different strains of A. minutum, the first producing both PST and BEC and the second producing only BEC. Escape response to starfish, daily shell growth, histological effects, and accumulation of PST were recorded after one week of exposure, and after two subsequent weeks of recovery. Daily shell growth was delayed three days in scallops exposed to the BEC-producing A. minutum strain, probably during the three first days of exposure. An increase of reaction time to predators was observed in scallops exposed to the BEC condition, suggesting that BEC may have altered sensing processes. Scallops exposed to PST displayed a less-efficient escape response and muscular damage which could reflect the effects of paralytic toxins upon the nervous system of scallops. This study demonstrates contrasting effects of the distinct toxic compounds produced by A. minutum upon marine bivalves, thus highlighting the importance to better characterize these extracellular, bioactive compounds to better understand responses of other marine organisms.

Dinoflagellates of the genus Alexandrium are a major cause of harmful algal blooms (HABs) that have increasingly disrupted coastal ecosystems for the last several decades. Microalgae from the genus Alexandrium are known to produce paralytic shellfish toxins (PST) but also bioactive extracellular compounds (BEC) that can display cytotoxic, allelopathic, ichtyotoxic or haemolytic effects upon marine organisms. The objective of this experimental study was to assess the effects of PST and BEC produced by A. minutum upon juvenile great scallops Pecten maximus. Scallops were exposed for one week to two different strains of A. minutum, the first producing both PST and BEC and the second producing only BEC. Escape response to starfish, daily shell growth, histological effects, and accumulation of PST were recorded after one week of exposure, and after two subsequent weeks of recovery. Daily shell growth was delayed three days in scallops exposed to the BEC-producing A. minutum strain, probably during the three first days of exposure. An increase of reaction time to predators was observed in scallops exposed to the BEC condition, suggesting that BEC may have altered sensing processes. Scallops exposed to PST displayed a less-efficient escape response and muscular damage which could reflect the effects of paralytic toxins upon the nervous system of scallops. This study demonstrates contrasting effects of the distinct toxic compounds produced by A. minutum upon marine bivalves, thus highlighting the importance to better characterize these extracellular, bioactive compounds to better understand responses of other marine organisms.